3.13.11.6 -stable review patch.  If anyone has any objections, please let me 
know.

------------------

From: Mateusz Guzik <[email protected]>

commit b0ab99e7736af88b8ac1b7ae50ea287fffa2badc upstream.

proc_sched_show_task() does:

  if (nr_switches)
        do_div(avg_atom, nr_switches);

nr_switches is unsigned long and do_div truncates it to 32 bits, which
means it can test non-zero on e.g. x86-64 and be truncated to zero for
division.

Fix the problem by using div64_ul() instead.

As a side effect calculations of avg_atom for big nr_switches are now correct.

Signed-off-by: Mateusz Guzik <[email protected]>
Signed-off-by: Peter Zijlstra <[email protected]>
Cc: Linus Torvalds <[email protected]>
Link: 
http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
Signed-off-by: Kamal Mostafa <[email protected]>
---
 kernel/sched/debug.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index 5c34d18..0c60913 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -608,7 +608,7 @@ void proc_sched_show_task(struct task_struct *p, struct 
seq_file *m)
 
                avg_atom = p->se.sum_exec_runtime;
                if (nr_switches)
-                       do_div(avg_atom, nr_switches);
+                       avg_atom = div64_ul(avg_atom, nr_switches);
                else
                        avg_atom = -1LL;
 
-- 
1.9.1

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